Preheat oven to 400°F.
Brown ground beef and onion in skillet over medium heat 8-10
minutes or to 160°F doneness.
Pour off drippings and blot with paper towel. Stir in oregano.
Lightly brush tortillas with oil. Bake tortillas on 2 large
baking sheets in 400ºF oven for 3 minutes.
Spoon beef mixture evenly over top of each tortilla. Top with an
equal amount of tomato. Sprinkle with basil and cheeses.
Return to oven and bake 12-14 minutes or until tortillas are
lightly browned.